Method and apparatus of a moile communication system which reduces power comsumption by observing only the starting slot on a tdma radio channel

ABSTRACT

Base station generates a mobile station identifier which indicates a mobile station that a data signal is addressed thereto, and a head slot having a data signal when there is a data signal that has a length to be able to transmitted using one slot of a TDMA radio channel. When there is a data signal that has a length to be not able to transmitted using one slot, base station generates a head slot and continuous slots which contain at least a part of data signal. Base station transmits the head slot by using the starting slot which located at predetermined position every mobile station on the TDMA radio channel, and transmits the continuous slots by using slots which follow the starting slot. Mobile station receives the starting slot, and stops reception if the starting slot is not the head slot. If the starting slot is the head slot, the mobile station judges the mobile station identifier. Furthermore, if the mobile station identifier indicates other mobile station, the mobile station stops reception, on the other hand, if the mobile station identifier indicates itself, the mobile station receives the continuous slot.

TECHNICAL FIELD

[0001] The present invention relates to a mobile communication systemwhich communicates between a base station and a plurality of mobilestations using a TDMA method, and particularly, to a mobilecommunication system which is able to reduce the electrical powerconsumed by mobile station which employs a TDMA method to receive datasignals.

BACKGROUND ART

[0002] In the conventional technology, when a data signal for a mobilestation is generated, a base station that communicates using a TDMAmethod searches for a vacant slot in the TDMA channels, and transmitsthe data signal from the vacant slot immediately after generation of thedata signal. Meanwhile, a mobile station monitors all slots, andreceives the data signal in a given slot if that data signal isaddressed to that station.

[0003] In this case, however, the mobile station must demodulate everyreceived slot to determine whether or not its own data signal iscontained therein. Furthermore, the mobile station must judge whether adata signal is addressed to itself or not, by reading out the mobileidentifier which is contained in each slot. Electrical power istherefore consumed by the mobile station in carrying out the abovementioned procedures. At the same time, it is necessary to extend thesignal waiting time of the mobile station, and to reduce the size of themobile station's battery. In order to meet these requirements, it isthus desirable to reduce as much as possible the electrical power usedin data signal detection.

DISCLOSURE OF INVENTION

[0004] The present invention was developed in consideration of the abovecircumstances, and has as its objective the provision of a mobilecommunication system wherein it is possible to reduce the electricalpower consumed by the mobile station during the signal reception waitingperiod, by observing only the starting slot of a TDMA radio channel.

[0005] (1) A mobile communication system that transmits data signal frombase station to a plurality of mobile stations by using TDMA radiochannel that consists of a plurality of slots; wherein

[0006] said base station consists of

[0007] a generating means for generating a head slot having a mobilestation identifier which indicates a mobile station for transmission andcontinuous slots having a least part of said data signal,

[0008] a transmission means for transmitting said head slot withstarting slot which locates at predetermined position each of said aplurality of mobile stations, on said TDMA radio channel, and

[0009] a transmission for transmitting said continuous slot with slotwhich continues said starting slot,

[0010] each of said mobile stations consists of

[0011] a observation means for observing said starting slot,

[0012] a judging means for judging said mobile station identifier whensaid starting slot is a head slot,

[0013] a receiving means for receiving said continuous slot when saidmobile station identifier indicates oneself.

[0014] Therefore, according to the present invention, a mobile stationmonitors only a starting slot, so that it is possible to reduce theelectrical power of the battery consumed by the mobile station to beshorten the operating time of a receiving apparatus, in comparison within case where the mobile station monitors all slots.

[0015] (2) Said base station further consists of a transmission meansfor transmitting vacant slot which does not contain said data signalwhen there is no said data signal,

[0016] said mobile station further consists of a stopping means forstopping a receiving operation until next of said starting slot whensaid starting slot is said vacant slot or said continuous slot.

[0017] Therefore, according to the present invention, when the receivedslot is a vacant slot or when received slot is a signal slot addressedto other mobile station, the mobile station stops reception of signal,so that it is possible to be shorten a delay time of the signal bytransmitting continuously a plurality of signals.

[0018] (3) Said base station further consists of a generating means forgenerating synchronous words of various kinds which is for synchronizingto said slots,

[0019] a transmission means for transmitting a synchronous word selectedfrom said synchronous words of various kinds to contain in said slots,on the basis of the information which indicates whether the monitoredslot is said starting slot or not, said mobile stations further consistsof a judging whether said slot is said starting slot or not, on thebasis of the kind of said synchronous word.

[0020] Therefore, according to the present invention, the mobile stationcan judge the position of the starting slot at the same time assynchronizing of slots.

[0021] (4) Base station sets a common starting slot at a predeterminedposition on said TDMA radio channel, and farther consists of agenerating means for a continuous slot having mobile station identifierswhich indicate said plurality of mobile stations and at least a part ofsaid data signal when said base station transmits common data signal fora plurality of mobile stations,

[0022] a transmission means for transmitting said starting slot withsaid common starting slot,

[0023] a transmission means for transmitting said continuous slot withsaid slots which follows said common starting slot,

[0024] said mobile station further consists of a monitoring means formonitoring said common starting slot, in addition to said starting slotwhich determined for every mobile station,

[0025] a recognition means for recognizing said mobile stationidentifier when said common starting slot is said starting slot,

[0026] a receiving means for receiving said continuous slot if there isa mobile station identifier which indicates itself among said mobilestation identifiers.

[0027] Therefore, according to the present invention, it is possible toreduce the electrical power of the battery consumed by the mobilestation, and to ensure signal transmission addressed to each mobilestation by arranging to disperse slot of each mobile station.Furthermore, it is possible to shorten a delay time wherein a commonsignal is transmitted to a plurality of mobile stations by set a commonstarting slot that a plurality of mobile stations begin receptioncommonly, in comparison with the case where an individual slot is usedeach mobile station. In addition, it is possible to improve the usingefficiency of the TDMA radio channel by that over-lapped signal does nottransmit.

[0028] (5) Said base station further consists of a transmission meansfor transmitting a informing signal indicating a position of saidstarting slot for each of mobile stations,

[0029] said mobile station further consists of a starting means forstarting a receiving operation from said starting slot which isindicated by said information signal.

[0030] Therefore, according to the present invention, it is possible toinform immediately presence of data signal to the mobile station, incomparison with the case where data signals are transmitted successivelyto one or more mobile stations, by informing presence of data signal toone or more mobile stations with the informing signal.

[0031] (6) Said mobile station further consists of a transmission meansfor transmitting a receiving mode which indicates whether it monitorsall slots or it monitors only starting slot,

[0032] an observing means for observing said slot by the receiving modewhich is transmitted by said transmission means,

[0033] said base station further consists of a receiving means forreceiving said receiving mode,

[0034] a transmission means for transmitting said data signal to amobile station which transmits said receiving mode from a slotimmediately after that said data signal is generated, when saidreceiving mode indicates to monitor said all slots,

[0035] a transmission means for transmitting said data signal for amobile station which transmitted said receiving mode from said startingslot when said receiving mode indicates that said mobile stationmonitors only said starting slot.

[0036] Therefore, according to the present invention, it is possible toswitch a transmission mode by request from the mobile station in thebase station. Furthermore, it is possible to immediately transmit datasignal by switching a succession transmission mode, in the case wherethe traffic is large or the permitted transmission delay is small. Inaddition, it is possible to change a transmission procedure to theintermittent transmission mode at the start of communication or duringcommunication, according to the limit of the battery consumption in themobile station.

[0037] (7) Said base station further consists of a transmission meansfor transmitting a slot designating signal which contains informationindicating a position of said starting slot,

[0038] said mobile station further consists of a receiving means forreceiving said slot designating signal,

[0039] a judgment means for judging a position of said starting slotbased on said slot designating signal.

[0040] Therefore, according to the present invention, it is possible todetermine the arrangement of the starting slot and the common startingslot, according to the conditions.

BRIEF DESCRIPTION OF DRAWINGS

[0041]FIG. 1 is a block diagram showing the structure of a communicationsystem of a first embodiment in this invention;

[0042]FIG. 2 is a conceptual diagram showing the structure of datasignal 32;

[0043]FIG. 3 is a conceptual diagram showing the structure of TDMA radiochannel 30;

[0044]FIG. 4 is a conceptual diagram showing the structure of a vacantslot;

[0045]FIG. 5 is a conceptual diagram showing the structure of a signalslot used for transmitting a data signal;

[0046]FIG. 6 is a conceptual diagram showing a transmission method ofthe vacant slot and the signal slot in the TDMA radio channel;

[0047]FIG. 7 is a conceptual diagram showing the procedures of areceiving apparatus wherein there is no signal to be transmitted from abase station to mobile stations;

[0048]FIG. 8 is a conceptual diagram showing the procedures of areceiving apparatus wherein the starting slots are arranged periodicallyon TDMA radio channel;

[0049]FIG. 9 is a conceptual diagram showing the procedures of areceiving apparatus wherein there is a signal to be transmitted from abase station to mobile stations;

[0050]FIG. 10 is a conceptual diagram showing the method for determiningthe position of the starting slot at the mobile stations;

[0051]FIG. 11 is a conceptual diagram showing the procedures of themobile stations wherein there are two or more signals to be transmittedfrom a base station to a mobile station;

[0052]FIG. 12 is a conceptual diagram showing an example of theprocedures of a base station and a plurality of mobile stations;

[0053]FIG. 13 is a conceptual diagram showing the procedures of a basestation and a mobile station wherein the base station transmits a commonsignal to a plurality of mobile stations;

[0054]FIG. 14 is a conceptual diagram showing the structure of atransmission mode signal;

[0055]FIG. 15 is a conceptual diagram showing the structure of aninforming signal;

[0056]FIG. 16 is a conceptual diagram showing the structure of a datasignal;

[0057]FIG. 17 is a conceptual diagram showing the procedures of mobilestations in the case where the arrangement of the starting slots isinformed by means of an informing signal; and

[0058]FIG. 18 is a conceptual diagram showing the structure of a slotdesignation signal, which designates the arrangement of starting slotsor a common starting slot.

BEST MODE FOR CARRYING OUT THE INVENTION

[0059] The best mode for carrying out the present invention will now bedescribed with reference to the drawings.

[0060] First Embodiment

[0061] A. Hardware Structure of First Embodiment

[0062]FIG. 1 is a block diagram showing the structure of thecommunication system of a first embodiment in this invention. In FIG. 1,base station 10 and one or more mobile stations 20, 21 are set up in amobile communication system. Base station 10 and mobile stations 20, 21communicate through a TDMA radio channel. Base station 10 consists oftransmission apparatus 11, which transmits TDMA radio channel 30, andcontrol apparatus 12, which controls the operation of transmissionapparatus 11 by generating a signal. Mobile station 20 consists ofreceiving apparatus 23, which receives TDMA radio channel 30, andcontrol apparatus 22, which controls the operation of receivingapparatus 23 by analyzing the signal.

[0063] B. Data Structure in First Embodiment

[0064] An explanation will be made of various data structures which areused in the first embodiment. FIG. 2 is a conceptual diagram showing thestructure of data signal 32 which is transmitted from base station 10 tomobile stations 20, 21. Data signal 32 consists of mobile stationidentifier 34, which indicates an address, and data 36, which istransmitted to mobile stations 20, 21.

[0065]FIG. 3 is a conceptual diagram showing the structure of TDMA radiochannel 30. TDMA radio channel 30 consists of continuous slots 40. Aslot 40 consists of slot type 41 which indicates the type of slot,continuous slot number 42 which indicates the number of slots which arecontinuous to form data signal 32, and signal part 43. Data signal 32 isinserted into one or more signal parts 43.

[0066]FIG. 4 is a conceptual diagram showing the structure of a vacantslot 40 where a data signal is not contained. Slot type 41 indicatesthat the slot is a vacant slot, and continuous slot number 42 indicates“0”. Signal part 43 is not used.

[0067] Next, FIG. 5(A) is a conceptual diagram showing the structure ofa signal slot wherein data signal 32 is transmitted by using a pluralityof slots. In a head slot, slot type 41 indicates that the slot is a headslot. Furthermore, the number of slots which continue after the headslot, i.e. “3”, is inserted into continuous slot number 42. The headportion of data signal 32 is set in signal part 43. Next, slot type 41of the continuous slots indicates that the slots are continuous slots.The remaining portion of data signal 32 is set in signal part 43 of thecontinuous slots.

[0068] However, it is possible to transmit data signal 32 with one slot.In this case, only a single slot as shown in FIG. 5(B) is transmitted.Slot type 41 of this slot indicates that the slot is the head slot, andthe number of continuous slots 42 is “0”.

[0069] Next, FIG. 6 is a conceptual diagram showing the state wherein avacant slot having no data signal 32 and a signal slot having a signalare transmitted through the TDMA radio channel. In FIG. 6, the hatchedslots are signal slots, while the slots without hatching are vacantslots. When data signal 32 is generated, a signal slot or a plurality ofsignal slots corresponding to data signal 32 is transmittedcontinuously. The vacant slots are transmitted during the period whensignal slots are not transmitted.

[0070] C. Operation of First Embodiment

[0071] C.1. Monitoring by Mobile Station for Data Addressed to Itself

[0072]FIG. 7 is a conceptual diagram showing the procedures of basestation 10 in the case where there is no signal to be transmitted. Inthis case, control apparatus 12 causes transmission apparatus 11 totransmit vacant slots in all slots of TDMA radio channel 30. The slotherein is assumed to be generated at a fixed timing in TDMA radiochannel 30. This slot is called the “starting slot”. When controlapparatus 21 of mobile stations 20, 21 receives starting slot 90,control apparatus 21 outputs instructions to receiving apparatus 23 tostart receiving.

[0073] Receiving apparatus 23 receives starting slot 90 when it receivesthe instructions, and supplies the starting slot 90 to control apparatus22. Control apparatus 22 detects whether supplied starting slot 90 is avacant slot or not. If starting slot 90 is a vacant slot, controlapparatus 22 judges that a signal addressed to itself has not occurred,and instructs receiving apparatus 23 to stop receiving the slots.

[0074] Starting slot 90 is arranged periodically on TDMA radio channel30 as shown in FIG. 8. Therefore, mobile stations 20, 21 may monitoronly starting slot 90.

[0075] C.2. Data Transmission (Single) for Mobile Station

[0076] An explanation will now be made of the operation when variousdata are transmitted to mobile stations 20, 21, beginning with the casewhere the data signal to be transmitted is a singular number.

[0077] As shown in FIG. 9, base station transmits a signal generatedprior to the occurrence of a given starting slot 90 as the startingpoint for starting slot 90. For example, when data signal 32 to betransmitted to mobile station 20 occurs at time t10, control apparatus12 of base station 10 holds the transmission of data signal 32 untiltransmission starting time t11 of starting slot 90. Next, controlapparatus 12 causes transmission apparatus 11 to transmit vacant slotsuntil the slot immediately preceding starting slot 90, and to start thetransmission of data signal 32 from starting slot 90. When transmissionapparatus 11 completes the transmission of data signal 32, controlapparatus 12 causes transmission apparatus 11 to transmit vacant slots.

[0078] Control apparatuses 22, 22 of mobile stations 20, 21 instructreceiving apparatuses 23, 23 to start signal reception at starting slot90. Consequently, receiving apparatuses 23, 23 receive the informationin starting slot 90, and supply the information to control apparatuses22, 22. Control apparatuses 22, 22 determine whether to continuereceiving the signals or not, based on the slot received from receivingapparatuses 23, 23. That is, control apparatuses 22, 22 continue signalreception if the received slot is the starting slot of data signal 32addressed to that mobile station. After that, control apparatuses 22, 22instruct receiving apparatuses 23, 23 to stop signal reception aftercompletion of reception of the signal slot containing data signal 32. Onthe other hand, if starting slot 90 is a vacant slot or is a slot havinga data signal for another station, then signal reception is terminated.

[0079] An explanation using FIG. 10 will now be made of the method bywhich mobile stations 20, 21 determine the position of starting slot 90on TDMA radio channel 30. First, each slot contains a synchronous wordso that mobile stations 20, 21 can synchronize with the slots. Whencommunication is started, mobile stations 20, 21 continuously receivethe slots of TDMA radio channel 30, and synchronize with these slots. Inthis embodiment, two types of synchronous words 50, 52 are employed.Base station 10 transmits synchronous word 50 with slot 90, andtransmits synchronous word 52 with another slot. Mobile stations 20, 21continuously receive slots at the start of communications, and determinethat “the slot in which synchronous word 50 was received is startingslot 90”. Consequently, mobile stations 20, 21 can synchronize with theslots, while simultaneously determining the position of starting slot90.

[0080] In the above mentioned operation, the position of starting slot90 may be determined dynamically based on the transmission delay of theforward signal required by mobile stations 20, 21 and the amount ofstored energy consumed in the battery. For example, in the case wherethere is a low volume of signal traffic, and a large delay is permittedbetween the occurrence of a signal in base station 10 and thetransmission of the signal to mobile stations 20, 21, then the intervalof starting slot 90 may be larger. Conversely, when a large delay is notpermitted, then the interval of starting slot 90 may be shorter.

[0081] In the above mentioned operation, mobile stations 20, 21 monitoronly starting slot 90, so that the operating time of receiving apparatus23 becomes shorter than it is in the case when all slots are monitored.Therefore, it is possible to reduce battery consumption in mobilestations 20, 21.

[0082] C.3. Data Transmission (Plural) for Mobile Station

[0083] Next, an explanation will be made of the operation in the casewhere a plurality of data signals 32 are transmitted from base station10 to mobile stations 20, 21. FIG. 11 is conceptual diagrams showing thestate where two data signals 32 to be transmitted from base station 10are present. In base station 10, when two data signals 32 occur, controlapparatus 12 holds the transmission of data signal 32 until thetransmission of starting slot 90 is started. Next, control apparatus 12instructs transmission apparatus 11 to transmit the signal slotscontaining two data signals 32 from starting slot 90, and two datasignals 32 are transmitted from transmission apparatus 11. When thetransmission of the signal slots is complete, control apparatus 12causes transmission apparatus 11 to transmit vacant slots.

[0084] Receiving apparatuses 23, 23 of mobile stations 20, 21 startreception of the signal from starting slot 90, and transmit the receivedsignal to control apparatuses 22, 22. Next, control apparatuses 22, 22determine whether to continue receiving or not based on the slotreceived from receiving apparatuses 23, 23. That is, if the mobileidentifier 34 for that mobile station is included in signal part 43 ofthe starting slot, then control apparatuses 22, 22 instruct receivingapparatuses 23, 23 to receive the number of continuous slots which isindicated by continuous slot number 42. Receiving apparatuses 23, 23receive the consecutive continuous slots according to the instructions.Furthermore, after reception of the consecutive continuous slots,receiving apparatuses 23, 23 receive another slot. If this slot containsa mobile identifier 34 that indicates that mobile station, thenreceiving apparatuses 23, 23 further receive the number of continuousslots which is indicated by continuous slot number 42.

[0085] On the other hand, if the received slot is a vacant slot or isfor another mobile station, then control apparatuses 22, 22 instructreceiving apparatuses 23, 23 to stop signal reception. Therefore, as aresult of the above-mentioned operation, it is possible to shorten thedelay time of the signal by consecutively transmitting a plurality ofsignals.

[0086] C.4. Volley Informing

[0087] Next, an explanation will be made with reference to FIGS. 12 and13 of a volley informing operation in which a common signal istransmitted to a plurality of mobile stations. As shown FIG. 12, basestation 10 transmits signals for mobile station 20 from starting slot90, and transmits signals for mobile station 21 from starting slot 91.Starting slot 91 has the same data structure as starting slot 90. Mobilestation 20 monitors starting slot 90, and mobile station 21 monitorsstarting slot 91.

[0088] As shown in FIG. 13, base station 10 transmits data signal 32which will be transmitted to both mobile station 20 and mobile stations21, from common starting slot 95. Mobile station identifier 34 of datasignal 32 indicates both mobile station 20 and mobile station 21. Notethat here the position of common starting slot 95 on the TDMA radiochannel is determined in advance. Mobile stations 20, 21 monitor commonstarting slot 95, in addition to starting slot 90 or 91. If commonstarting slot 95 contains a signal addressed to itself, then mobilestations 20, 21 stop reception after receiving the signal slots whichfollow common starting slot 95. On the other hand, if the received slotis a vacant slot or a signal slot for another mobile station, thenmobile stations 20, 21 stop reception immediately.

[0089] As a result of the above described operation, it is possible toreduce the amount of stored energy consumed in the battery of the mobilestation, while ensuring signal transmission for each mobile station, byarranging diffusely the slots for each mobile station. Furthermore, itis possible to shorten the delay time in the case where a common signalis transmitted to a plurality of mobile stations by providing commonstarting slot 95 which a plurality of mobile stations begin signalreception in common, as compared to the delay time in the case where anindividual slot is used for each mobile station. In addition, it ispossible to improve the utilization efficiency of the TDMA radio channel30 because there is no over-lapped signal transmission.

[0090] C.5. Mode Switching

[0091] A conventional mobile station continuously monitors a TDMA radiochannel. In the present invention, it is of course acceptable to mix aconventional mobile station and a mobile station which monitors onlystarting slot 90 based on this embodiment in the communication system.On the other hand, in the mobile station according to this embodiment,if the traffic volume is large, or if the permissible transmission delayis short, then it is optimal for the mobile station to be able tocontinuously monitor TDMA radio channel 30.

[0092] Thus, in this embodiment, in that case, it is possible to switchthe operating mode of mobile stations 20, 21 based on the control ofbase station 10, and to change the transmission mode of base station 10.Furthermore, conversely, base station 10 may switch the transmissionmode according to a request from mobile stations 20, 21.

[0093]FIG. 14 is a conceptual diagram showing the structure oftransmission mode signal 87 which requests the switching of thetransmission mode from mobile stations 20, 21 to base station 10.Transmission mode signal 87 consists of mobile station identifier 34,signal type 82 showing that the signal is the transmission mode signal,and transmission mode information 88 showing the transmission procedureof the signal. Transmission mode information 88 indicates a continuationtransmission mode and an intermittent transmission mode, for example. Inthe continuous transmission mode, the transmission of data signalsstarts at an optional time. In the intermittent transmission mode, thetransmission of data signals starts with starting slot 90 and commonstarting slot 95 only. Meanwhile, mobile stations 20, 21 transmittransmission mode signal 87 to base station 10 before a communication orduring a communication. When base station 10 receives transmission modesignal 87, base station 10 transmits data signals according to thetransmission procedure requested by mobile station 20 or 21.

[0094] By the above mentioned operation, in the case where the volume oftraffic is large, or the permissible transmission delay is small, it ispossible to carry out transmission at a high rate in the same way as theconventional technique, by switching to the continuous transmissionmode. Furthermore, it is possible to change the transmission procedureto the intermittent transmission mode at the start of communication orduring communication, according to the limit of the battery consumptionin the mobile station. In addition, it is possible to change theinterval of the starting slot based on transmission mode signal 87.

[0095] Furthermore, in the first embodiment, although base station 10 isrequested by mobile stations 20, 21 to change of the transmission mode,it is also acceptable for base station 10 to switch the transmissionmode of each mobile station 20, 21. In this case, base station 10switches the transmission mode according to a list (table), which isstored therein in advance and has compatible transmission modes for eachmobile station 20, 21. Each of mobile stations 20, 21 is given anintrinsic mobile identifier respectively, so that base station 10 maystore the transmission mode of each mobile station corresponding to themobile identifier. The information in the list is set by some inputmeans or other in advance.

[0096] Second Embodiment

[0097] A. Hardware Structure and Data Structure of Second Embodiment

[0098] The hardware structure of the second embodiment is the same asthat of the first embodiment, however, the data structure differsslightly, as described below.

[0099] That is, in this second embodiment, starting slot information 85showing the position of starting slot 90 in each mobile station istransmitted from base station 10 to mobile stations 20, 21 by informingsignal 80. Base station 10 transmits one or more data signal 86 tomobile stations 20, 21 after transmission of informing signal 80.

[0100]FIG. 15 is a conceptual diagram showing the structure of informingsignal 80. Informing signal 80 consists of mobile station identifier 34for identifying one or more mobile stations which are to receive theinforming signal, signal type 82 which indicates that it is an informingsignal, and mobile station identifier list 83. Mobile station identifierlist 83 contains individual mobile station identifier 84 which indicateseach address of one or more signals, and starting slot ion 85 whichindicates the position of the starting slot of data signal 86.

[0101]FIG. 16 is a conceptual diagram showing the structure of datasignal 86. Data signal 86 consists of mobile station identifier 34 foridentifying a mobile station, signal type 82 which indicates that it isa data signal, and data 36.

[0102] B. Operation of Second Embodiment

[0103] Next, an explanation will be made of the operation of basestation 10 and mobile station 20 with reference to FIG. 17. First, basestation 10 starts to transmit informing signal 80 with common startingslot 95. Meanwhile, mobile station 20 and mobile station 21 start toreceive with common starting slot 95. If signal type 82 of the receivedsignal indicates an informing signal, then mobile station 20 or 21 readsout starting slot information 85 which follows the individual mobilestation identifier 84 for that station.

[0104] When data signal 86 for base station 20 and data signal 86 formobile station 21 are generated, base station 10 generates mobilestation identifier 34 indicating that mobile stations 20, 21 shouldcarry out signal reception, individual mobile station identifier 84 andstarting slot information 85 of mobile station 20, and informing signal80 which consists of individual mobile station identifier 84 andstarting slot information 85 for mobile station 21, and transmits thesesignals from common starting slot 95. Next, base station 10 transmitsdata signal 86 for mobile station 20 from starting slot 90 which isindicated by starting slot information 85 which follows the individualmobile station identifier 84 for mobile station 20. Furthermore, basestation 10 transmits data signal 86 for mobile station 21 from startingslot 91 which is indicated by starting slot information 85 which followsthe individual mobile station identifier 84 for mobile station 21. Datasignal 86 is transmitted by one slot or a plurality of slots in the samemanner as shown in FIG. 5.

[0105] Mobile station 20 begins receiving the signal from starting slot90 which is indicated by starting slot information 85 which follows theindividual mobile station identifier 84 for mobile station 20. If thereceived slot is one which is addressed to that station, then mobilestation 20 continues signal reception. On the other hand, if thereceived slot is vacant, or is a signal slot addressed to anotherstation, then mobile station 20 halts signal reception.

[0106] An explanation will now be made of how starting slot 90 maybecome a slot for another station. A starting slot is assigned to everymobile station, so that, in general, the reception of information iscomplete before the generation of a starting slot for another stationoccurs. However, when the interval between starting slots becomes narrowdue to an increase in the number of mobile stations in an area, or thetraffic for a specific mobile station increases notably, the slot of thespecific mobile station is extended to the next starting slot which hasbeen generated for another station.

[0107] In the example shown in FIG. 17, starting slot 90 is the nextslot after common starting slot 95, so that mobile station 20 receivesdata signal 86 in succession after informing signal 80. After that,mobile station 20 stops the reception of the data signal. Furthermore,starting slot 91 is separated from common slot 95, so that mobilestation 21 receives informing signal 80, and then terminates receptionafter that. Next, mobile station 21 starts to receive slots fromstarting slot 91 again. Further, mobile station 21 stops reception afterreceiving data signal 86.

[0108] In this second embodiment, the presence of a data signal isinformed to one or more mobile stations by informing signal 80, so thatit is possible to inform a mobile station of the presence or absence ofa data signal more quickly as compared to the case where signals aretransmitted successively to one or more mobile stations. Furthermore, itis possible to improve the utilization efficiency of the TDMA radiochannel.

[0109] Variations of Present Invention

[0110] This invention may be practiced or embodied in still other wayswithout departing from the spirit or essential character thereof.Therefore, the preferred embodiments described herein are illustrativeand not restrictive, the scope of the invention being indicated by theappended claims and all variations which come within the meaning of theclaims are intended to be embraced therein.

[0111] For example, it is possible to realize various modifications asfollows. i) Base station 10 may determine the arrangement of startingslots 90, 91 and common starting slot 95 by fixed algorithm. In thiscase, base station 10 may inform the arrangement of starting slots 90,91 in the first embodiment and the arrangement of common starting slot95 in the first and second embodiment, to mobile stations 20, 21 withslot designation signal 60.

[0112]FIG. 18 is a conceptual diagram showing slot designation signal60. Slot designation signal 60 consists of mobile station identifier 37for identifying mobile station 20, signal type 82 which indicates thatit is slot designation signal 60, and slot information 62. Slotinformation 62 indicates the arrangement of starting slots 90, 91 in thefirst embodiment and the arrangement of common starting slot 95 in thefirst and second embodiment.

[0113] Base station 10, for example, determines the arrangement ofstarting slots 90, 91 and common starting slot 95 to increase theutilization efficiency of the radio channel by using parameters. Forexample, the parameters consist of the number of mobile stations, thepermitted transmission delay, the amount of the individual signal foreach mobile station, the amount of the common signal for a plurality ofmobile stations, the occurrence characteristic of the signal, and so on.

[0114] ii) Slot designation signal 60 may be transmitted using a TDMAradio channel used for control which is different from a TDMA radiochannel used for communication. In this case, mobile stations 20, 21switch to a TDMA radio channel used for communication after they receiveslot designation signal 60 with a TDMA radio channel for control. Afterthat, mobile stations 20, 21 monitor designated starting slots 90, 91and common starting slot 95. Therefore, it is possible to flexiblydetermine the arrangement of starting slots 90, 91 and common startingslot 95, according to conditions. In addition, mobile station 20 maydetermine starting slots 90, 91 and common starting slot 95, and mayinform base station 10.

1. A mobile communication system that transmits data signal from basestation to a plurality of mobile stations by using TDMA radio channelthat consists of a plurality of slots; wherein said base stationconsists of a generating means for generating a head slot having amobile station identifier which indicates a mobile station fortransmission and continuous slots having a least part of said datasignal, a transmission means for transmitting said head slot withstarting slot which locates at predetermined position each of said aplurality of mobile stations, on said TDMA radio channel, and atransmission for transmitting said continuous slot with slot whichcontinues said starting slot, each of said mobile stations consists of aobservation means for observing said starting slot, a judging means forjudging said mobile station identifier when said starting slot is a headslot, a receiving means for receiving said continuous slot when saidmobile station identifier indicates oneself.
 2. A mobile communicationsystem according to claim 1, wherein said base station further consistsof a transmission means for transmitting vacant slot which does notcontain said data signal when there is no said data signal, said mobilestation further consists of a stopping means for stopping a receivingoperation until next of said starting slot when said starting slot issaid vacant slot or said continuous slot.
 3. A mobile communicationsystem according to claim 1 or 2 either, wherein said starting slotcontains information which indicates the continuous number of saidcontinuous slot, said mobile station further consists of a receivingmeans for receiving said continuous slot until an end slot whichconsists of said data signal on the basis of the continuous number ofsaid continuous slot.
 4. A mobile communication system according toclaim 3, wherein said base station further consists of a generatingmeans for generating said head slot of a plurality of data signals andsaid continuous slot, a transmission means for transmitting continuouslysaid head slot of said plurality of data signal and said continuous slotwith said starting slot and a slot which continues said starting slot,said mobile station further consists of a receiving means for receivingnext slot of said end slot, a stopping means for stopping a receivingoperation when said next slot is not said head slot, a judging means forjudging said mobile station identifier when said next slot is said headslot, a receiving means for receiving a continuous slot which is followsaid head slot when said mobile station identifier indicates oneself,and for stopping the receiving operation when said mobile stationidentifier indicates another mobile station.
 5. A mobile communicationsystem according to claim 1, 2, 3 or 4 either, wherein said startingslot is arranged on said TDMA radio channel on the basis of the capacityof delay of said data signal and the traffic of said data signal.
 6. Amobile communication system according to claim 1, 2, 3, 4 or 5 either,wherein each of said starting slots for a plurality of said mobilestations is arranged on said TDMA radio channel, respectively.
 7. Amobile communication system according to claim 1, 2, 3, 4, 5 or 6either, wherein said base station further consists of a transmissionmeans for transmitting a informing signal indicating a position of saidstarting slot for each of mobile stations, said mobile station furtherconsists of a starting means for starting a receiving operation fromsaid starting slot which is indicated by said information signal.
 8. Amobile communication system according to claim 1, 2, 3, 4, 5, 6 or 7either, wherein said mobile communication system further comprising asecond mobile station which monitors all slots transmitted from saidbase station, said base station further consists of a transmission meansfor transmitting said data signal to said second mobile station with avacant slot immediately after that said data signal occurs.
 9. A mobilecommunication system according to claim 1, 2, 3, 4, 5, 6, 7 or 8 either,wherein said base station further consists of a holding means forstoring information which indicates whether each of a plurality of saidmobile stations has a first receiving mode or a second receiving mode, adiscrimination means for discriminating whether said mobile station hassaid first receiving mode or said second receiving mode, based on saidmobile station identifier of said mobile station, a transmission meansfor transmitting said data signal to said mobile station from a vacantslot immediately after that said data signal occurs when said mobilestation has said second receiving mode, a transmission means fortransmitting said data signal to said mobile station from said startingslot when said mobile station has said first receiving mode.
 10. Amobile communication system according to claim 9, wherein said mobilestation monitors only said starting slot in said first receiving mode,and monitors all slots in said second receiving mode.
 11. A mobilecommunication system according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10either, wherein said mobile station further consists of a transmissionmeans for transmitting a receiving mode which indicates whether itmonitors all slots or it monitors only starting slot, an observing meansfor observing said slot by the receiving mode which is transmitted bysaid transmission means, said base station further consists of areceiving means for receiving said receiving mode, a transmission meansfor transmitting said data signal to a mobile station which transmitssaid receiving mode from a slot immediately after that said data signalis generated, when said receiving mode indicates to monitor said allslots, a transmission means for transmitting said data signal for amobile station which transmitted said receiving mode from said startingslot when said receiving mode indicates that said mobile stationmonitors only said starting slot.
 12. A mobile communication systemaccording to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11 either, whereinsaid base station further consists of a generating means for generatingsynchronous words of various kinds which is for synchronizing to saidslots, a transmission means for transmitting a synchronous word selectedfrom said synchronous words of various kinds to contain in said slots,on the basis of the information which indicates whether the monitoredslot is said starting slot or not, said mobile stations further consistsof a judging whether said slot is said starting slot or not, on thebasis of the kind of said synchronous word.
 13. A mobile communicationsystem according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12either, wherein said base station further consists of a transmissionmeans for transmitting a slot designating signal which containsinformation indicating a position of said starting slot. said mobilestation further consists of a receiving means for receiving said slotdesignating signal, a judgment means for judging a position of saidstarting slot based on said slot designating signal.
 14. A mobilecommunication system according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11, 12 or 13 either, wherein base station sets a common starting slot ata predetermined position on said TDMA radio channel, and furtherconsists of a generating means for a continuous slot having mobilestation identifiers which indicate said plurality of mobile stations andat least a part of said data signal when said base station transmitscommon data signal for a plurality of mobile stations, a transmissionmeans for transmitting said starting slot with said common startingslot, a transmission means for transmitting said continuous slot withsaid slots which follows said common starting slot, said mobile stationfurther consists of a monitoring means for monitoring said commonstarting slot, in addition to said starting slot which determined forevery mobile station, a recognition means for recognizing said mobilestation identifier when said common starting slot is said starting slot,a receiving means for receiving said continuous slot if there is amobile station identifier which indicates itself among said mobilestation identifiers.